Assassin name : Childish Devil (Karma x OC)
by Demonic-Purity
Summary: A new student come at Kunugigaoka. Of course, this student got send into the End Class so "he" is necessarily an assassin ; the name that Rakuen Tokoyami got in this world : Childish Devil. Is this "Devil" able to kill Koro-sensei ? And what dark secrets does Tokoyami hide from most people ? What will Tokoyami do about it and how is this assassin going to act ?
1. Rakuen Tokoyami

_**Name :**_ Rakuen (means "Heaven")

 _ **First name :**_ Tokoyami (means "Eternal darkness")

 _ **Nickname**_ : You'll find out in the story.

 _ **Assassin name :**_ Childish Devil

 _ **Age :**_ 14

 _ **Birth date :**_ 21 June

 _ **Family :**_

 _ **.**_ Unnamed Father

 **.** Unnamed Mother (Deceased)

 **.** Cousin

 _ **Appearance :**_ Tokoyami has short dirty blonde and black hair and a fringe over the left eye with light gold. Tokoyami usually wears dark-colored clothes.

 _ **Height :**_ 160 cm (5'3")

 _ **Personality**_ : You'll find out in the story.

 _ **Extra :**_

-Loves music, singing and playing many instruments along with the dance to do shows because the mother of Tokoyami was an idol

-Is pretty good with electronic and coding.

-Have a childhood friend at Kunugigaoka + a cousin

-Is from a rich family

 **I tried tu put the less informations possible because I'm afraid to spoil something if I explain the OC's personality and background and I thought that it would be more enjoyable if you have everything in the story. I hope that you'll like it**.

 **And I would like to remind you that I'm Belgian so English isn't my mother-tongue and I don't own Ansatsu Kyoushitsu and the characters.**

 **You can also find this story on wattpad**


	2. Kunugigaoka's school

Tokoyami's POV :

I woke up to the sound of my alarm clock, it was 6:30 in the morning and today was supposed to be my first day at the most prestigious school Kunugigaoka. I quickly got up and prepared myself and before leaving my room to go downstairs I glanced at the poster of my deceased mother when she was an idol. My father was waiting for me and he looked pretty calm.

'The day's only starting Tokoyami.'

Once I was in front of my father I greeted him. "Good morning, Father." I bowed to him, he only nodded and patted me a little on the head. I stiffened slightly but he didn't notice.

"I will accompany you today to speak with the chairman. You must remember him, he is a friend Asano Gakuho." My father told me.

I nodded before answering "Yes, I remember. He has a son if I'm not mistaken so does that mean that we'll be in the same class ?"

"Since you did a full mark on the test you're in the A class, the same as Asano-kun."

"I see". 'Good to know.'

We went in the car, the ride for the school was quiet and I thought it was going to be like that until our arrival but my father spoke. "You can act whatever you want with Asano-kun but don't forget to be in the good sides of the others students, understood ?"

His tone implied that I should obey. "Yes father."

He nodded and the silence came back but we arrived a short time after, I caught a glimpse of strawberry blonde hair the second I stepped out of the car. I went to him and tapped him on the shoulder. "Long time no see Gakushuu-senpai."

The strawberry blonde male turned to me and slightly smiled. "Yeah, long time no see Tokoyami-kun. My father told me that we were going to be in the same class, it's good to hear." I only nodded in response and my father was beside us a second after.

"Hello to you Asano-kun. I hope you'll take good care of my son since he is the youngest in your year. If you'll excuse me I have to talk with you father." And with that he went his way, I heard Gakushuu sigh when he left. "I don't understand how you can live with this man Tokoyami."

"He's still my father. Even if... he changed" I trailed.

On our way I noticed a blue haired boy going farther then the main campus, at first I thought it was a girl because of his feminine look but he was wearing the boy's uniform so it was obvious. I stopped and Gakushuu stopped too.

"Nee Gakushuu-senpai, where is this guy going and who is he ?" I asked while pointing to the androgynous boy with pigtails. He looked at the direction I was pointing before looking at me with a scowl. "He is going to the mountain because the batiment for his class is there. He is a student from Class E. The End Class, you get there if you have bad grades or bad behavior."

I just nodded and replied with a monotone "I see."

Gakushuu continued to look at me for a moment before chluking "You're still as emotionless and monotone as ever."

I shrugged "If you say so..."

All day long I followed Gakushuu everywhere and talked when people came my way, after some time 4 guys came up to me and Gakushuu, I grimaced a bit when I saw their head. 'I never saw people THIS ugly until today !' Fortunately for me only my strawberry blonde childhood-friend noticed my grimace but I quickly regained my composure and I remarked that one of them looked alright. 'Thanks God.'

"Hello Asano-kun, who is this boy with you ?" The good-looking boy asked. He has brown hair that is fashioned into a kariage (clipped) hairstyle and dark, almond-shaped eyes.

"This is my childhood-friend Rakuen Tokoyami, Tokoyami-kun this is Sakakibara Ren. He is the Student Council secretary."

'Now it begins.' "Hello Sakakibara-senpai, it's a pleasure to meet you !" I exclaimed in a cheerful way that cause Gakushuu to look at me with slightly widened eyes.

"Nice to meet you too Rakuen-kun. And why did you call me senpai ?" Sakakibara asked.

"Because I'm one year younger than any other students of third year. I'm 14 after all." I answered while keeping my cheerful demeanour.

"YOU'RE 14 !?" All the students of the classroom exclaimed.

"Yep."

"You must be a true genius Rakuen-kun." Said Sakakibara while smiling at me.

"You can call me Tokoyami Sakakibara-senpai !" I said with a big grin.

"As you wish Tokoyami-kun."

And the day went on like that, everyone acknowledged me as a genius because I was the youngest and it got me a lot of respect from all the students of the main campus. After school I went back home, but I wasn't really expecting to see my father waiting for me with his arms crossed on his chest. 'What does he have to tell me now ? It's only my first day of school and something is already going to change.'

3rd person's POV :

Tokoyami put off his shoes before walking in front of his father. "What is it Father ?" "We have to talk. Come with me."

They went to the living-room and the both of them sat on a couch that were facing each other.

"I learned something very interesting when I talked with Gakuho. Do you remember what happened to the moon ?"

"70% of the moon got destroyed." He replied emotionless.

"That's right. Well, Gakuho told me that the cause of this was teaching Class E, and the cause is this."

The adult give his son a shit of paper with a picture of a yellow octupus whose face has green stripes. Tokoyami looked at it with a blank face before looking at his father. "And why is this octopus teaching the E Class ?" He questioned.

"We don't know but what is interesting is that the class have to kill him before March or else this thing is going to blow up the moon and the reward is 10 billion of yen. Since you are an assassin, you'll be transferring in the E Class and you, the Childish Devil is going to kill him so I'll get the money. Is that clear."

His tone clearly didn't let any choice to the boy so he only said "When did I start ?"

"Tomorrow."

And this is how Rakuen Tokoyami got into Class E with the mission of assassinate his new teaher.


	3. The End Class

The adult gave his son a shit of paper with a picture of a yellow octopus whose face has green stripes. Tokoyami looked at it with a blank face before looking at his father. "And why is this octopus teaching the E Class ?" He questioned.

"We don't know but what is interesting is that the class have to kill him before March or else this thing is going to blow up the moon and the reward is 10 billion of yen. Since you are an assassin, you'll be transferring in the E Class and you, the Childish Devil is going to kill him so I'll get the money. Is that clear."

His tone clearly didn't let any choice to the boy so he only said "When did I start ?"

"Tomorrow."

And this is how Rakuen Tokoyami got into Class E with the mission of assassinate his new teacher.

?'s POV :

I came early to climb the mountain since it's tiring but I'm used to it by now. When I sat down, I turned to my left to speak with my green haired classmate Kayano Kaede. She has hazel eyes, and green hair which is always fashioned in unique, cat ear-styled pigtailsand she is shorter than me by 4 inches.

"Hello Nagisa-kun !"

"Hello Kayano-chan." I greeted back.

A few more students entered the classroom and we chatted for awhile until Karma-kun came and put an octopus with a knife in his head on Koro-sensei's desk. Everyone got to their seats and we could sense a gloomy atmosphere in the room. Our yellow octopus teacher opened the door and greeted us with his usual smile.

"Hello minna-san !"

Seeing that we didn't greet back and sensing the tension in the piece Koro-sensei asked us what was wrong only to cut himself when he noticed the dead octopus on his desk.

"Oh ! Gomen gomen. I killed that thing mistaking it for you. Hand it to me I'll dispose it." Said Karma with a mischievous tone.

Koro-sensei did as said but then he disappeared one second to come back with a missile and some ingredients. Later on, Karma had a takoyaki in his mouth that Koro-sensei prepared at Mach 20 speed, Karma spilled the hot takoyaki.

"I could tell by your palor that you hadn't eaten breakfast. With these you'll be well on your way to being nice and healthy. Say 'haa'." Karma was narrowing his eyes at Koro-sensei .

"My job is to tend things, to take care of them. So keep your hardest to kill me today. Everytime you do, I'll take care of you. By the end of the day, your body and mind will be polished to sparking !" Koro-sensei give his usual wide grin to Karma before starting the class. A few minutes later, Karasuma-sensei came into the classroom.

3rd person's POV :

"Sorry to disturb the class. I came to tell you that you'll have a new student, he was in Class A but got removed here."

Everyone in the class got the same reaction "Eeehhhhhh !"

"You can enter now." Said Karasuma-sensei.

The door opened to reveal a man with dirty blonde hair and light gold eyes and beside him was a boy with the same eye and hair color but this boy had also black hair and his left eye was covered by his fringe, he was also wearing a black outfit consisting of black pants with a black belt that had a large silver buckle, a black V-necked shirt that was worn underneath a black trench-coat with gray lining going down the sleeves, and black boots with silver plates to protect his shins with a silver plate worn on on the left side of his coat, and a pair of black fingerless gloves and a strap that went over his right shoulder and under it to wrap around his left side instead of the uniform of the school.

"So it's you the teacher who destroyed the moon." Said the man while looking at Koro-sensei then he placed a hand on the boy's shoulder, he slightly stiffened but quickly gained his composure so no one really noticed. "This is my son Rakuen Tokoyami. I hope that you'll take great care of him." The man pushed his son forward so he was now in front of Koro-sensei.

"Hello to you Rakuen-kun. I'm Koro-sensei and I'll be your principal teacher and target."

The boy stared at him a few seconds before showing a bright smile. "Please call me Tokoyami and I hope that we'll spend a good year Koro-sensei." Exclaimed the blond boy while raising his hand for the teacher.

"Me too Tokoyami-kun." The octopus shook Tokoyami's hand but something that nobody expected happened. The boy pulled his teacher forward and took out a sword that was hidden in his outfit in a split of second 2 tentacles were on the floor and Koro-sensei jumped back in shock, Tokoyami got out his gun and began to shoot at Koro-sensei that was dodging the BB bullets. Tokoyami took this chance to go forward and sliced another tentacle, he was going straight to stab at the place where the black cravat was but a voice stopped him.

"That'll be enough Tokoyami."

Tokoyami's POV :

"That'll be enough Tokoyami."

I froze on the spot when I heard my father's voice. 'I did nothing wrong did I ?' I turned around and saw the whole class staring at me in awe. I took this opportunity to look at everyone and a girl with green hair caught my eye. 'She seems familiar.' I heard a few whispers in the classroom. "He is the second one to be successful to harm Koro-sensei."

"I'm the second one ? Then who is the first ?" I asked in curiosity.

I saw a red haired guy raise his hand in the back. "It was me Tokoyami-kun, you're jealous ?" 'This guy looked similar to Gakushuu, I didn't know he has a brother.'

"Why would I be jealous ?" I replied while tilting my head and giving a closed-eye smile. The class was silent until the boy next to Gakushuu's twin spoke in a rather irritating voice. "Don't be so cocky because you succeed to slice tentacles of this monster. It must have been luck."

I looked at my father from the corner of my eye to see him nod and in a split of second I was being this guy with my sword dangerously close to his throat, I put my head on his shoulder and I could feel the blade against my own throat and something hot dripping on my skin while I was pointing a gun at the teacher in front. "You could see that I know what I'm doing, simple because I'm not new when it comes to assassination." I paused to look at my victim's face, he was scared and sweat was rolling on his forehead I grin at that sight. "Now sensei~ What are you going to do ? You have two choices : letting me shot you or letting me slide this idiot throat and mine and let feel the despair of doing nothing to save your students." I said with a low voice.

"What are you planning to do Koro-sensei ?" Asked my father while turning to him but then the octopus disappeared and I was in the air with my hands and feet tied by... HIS TENTACLES ?! And the sword that I was using was also in one of his tentacle but he took it with a tissue.

"Congrats Tokoyami-kun, you quickly guessed that I had some conditions to respect as a teacher..." He said with an slightly orange face with a circle on it. "But... I can't let you harm yourself and your classmates." Now his face was purple with a big X on it, I 'tch'ed and he put me on the ground.

"Now that you see that, Tokoyami isn't like any of you in this class. He is a famous assassin known by the name of 'Childish Devil'. You're lucky to have someone with experience in this area. Now I'll take my leave." And my father did as he said and left the classroom, I got to my seat that was behind a gray haired boy.

Koro-sensei made us have a break after a few minutes because everyone were curious about me and next thing I knew, I was surrounded by everyone and replied to them with a warm smile and talking cheerfully with them when the green haired that caught my eye awhile ago grabbed my arm and dragged me outside, she turned to me and crossed her arms on her chest that is non existent if I can say.

"Do you know who I am ?" She asked me.

"Sorry but I didn't catch the name of everyone yet." I said while scratching the back of my head.

"I am Kayano Kaede." 'Kayano Kaede ? I'm sure that I heard it before but where ?' I stared at her face for a few seconds when it clicked.

"AKA-" I exclaimed but she cut me off by putting her hand over my mouth, I slightly glared at her and she immediately let go.

"Why are you here ?" We asked each other at the same time. "To kill this octopus" was both our answer.

"Revenge ?"I asked. She nodded.

"Your father ?" She asked, I sighed and passed my hand over my fringe. "You know the answer."

She looked at me with sad eyes then it was replaced by a frown. "Why do you act like that ? It doesn't look like you to be so cheerful."

"What do you think ?" I sarcastically replied to her, she scratched her head with a sheepish smile.

We went back in the classroom and everyone surrounded us while interrogating us on what was our relationship, I bounced on her to hug her and exclaimed. "She my cute cousin ! And I hope that none of you are doing anything bad to her." I finished with a dark aura around me. The boys answered negatively and my smile returned to my face then the blue haired boy that I saw yesterday and the red haired guy from earlier came at us.

"Nice to meet you Tokoyami-kun. I'm Nagisa Shiota and this Karma-kun." Introduced the androgynous boy. The red haired one known as Karma waved at me and I waved back.

"Nee Kayano-chan. Did you know that your cousin was an assassin ?" Karma asked.

"Umm... Yeah I knew."

The two boys stated at her in... confusion ? Or in surprise I would say.

"Nee Karma-senpai, I was wondering how did you injured Koro-sensei ?"

"Senpai ?" Asked the both of them while looking at me weirdly.

"Yes after all I'm only 14 so all of you are my senpai." I explained.

Everyone except Kaede reacted like that "Eeehhhhhh !?"

This is how went my first moment in the End Class and the day didn't really started since I interrupted the first hour and that we just had a break for everyone to talk to me.


	4. Karma's attempts

**"Nice to meet you Tokoyami-kun. I'm Nagisa Shiota and this is Karma-kun." Introduced the androgynous boy. The red haired one known as Karma waved at me and I waved back.** **"Nee Kayano-chan. Did you know that your cousin was an assassin ?" Karma asked.** **"Umm... Yeah I knew."** **The two boys stared at her in... confusion ? Or in surprise I would say.** **"Nee Karma-senpai, I was wondering how did you injured Koro-sensei ?** **"Senpai ?" Asked the both of them while looking at me weirdly.** **"Yes after all I'm only 14 so all of you are my senpai." I explained.** **Everyone except Kaede reacted like that "Eeehhhhhh !!??"** **This is how went my first moment in the End Class and the day didn't really started since I interrupted the first hour and that we just had a break for everyone to talk to me.**

Tokoyami's POV :

We all got back to our seats so Koro-sensei could truly began to do his job as a teacher and began the lesson from the corner of my eye I saw Karma taking out a gun from his vest and aim it at our teacher that was explaining how to remove a math formula but in a blink of an eye Koro-sensei had the gun and turned to Karma who had manicured nails, I chuckled and that earned me a glare from my senpai.

'First period : Math. Karma's first attempt : Failure.'

In fourth period, Koro-sensei was passing by the desk and came to our table. "How is your group doing Fuwa-san, Tokoyami-kun ?"

"It's good but I think it's still a bit spicy." She said.

I scratched my head with a sheepish smile. "Gomenasai I like spicy food."

Then Karma came beside us and I don't know why but I had a bad feeling for our soup. "Then you have to do it all over again and trash this one." He spilled the soup in the air.

"You forgot to wear your apron Karma-kun." Said Koro-sensei and Karma found himself with a pink frilly apron with a heart at the chest part and a pink bandana was on his head. I whistled at Karma like a hormonal boy would to a girl and snickered as I see a blush on his cheeks.

"Don't worry I got back the soup and I profited to put sugar in it." We tried the soup and smiled at its taste. "It's sweeter !" Exclaimed Fuwa-senpai. Karma was angrily putting the bandana off and growled when he heard Terasaka that I learned was the guy I threatened and it seemed to be the last one for Karma's limit as he tried to punch me but I dodged at the last moment and offered him a smile. "No need to be so angry Karma-senpai~" I said between my laughs.

'Fourth period : Home ec . Karma's second attempt : Failure.'

In fifth period we had Japanese but I didn't know if Karma tempted something since I was so tired that I took a nap.

3rd person's POV :

After Karma's failed attempt to kill Koro-sensei, this one noticed that his blonde student was sleeping and the rest of the class noticed that too.

"Ohhh he's so cute when he's sleeping~"

"You're so lucky to have him as your cousin Kayano-chan !"

"Move out guys I'll take a picture." Said Karma.

Everyone agreed and he did, Tokoyami woke up to the sound and looked to see that all eyes were on him. After that it was the lunch and Karma was the first one to get out of the classroom, Tokoyami decided to follow him to see him sitting on a branch that was on the end of the cliff. Tokoyami walked up to him and sat beside him on the tree.

Tokoyami's POV :

When I sat beside him, he was biting on his nails in frustration or anger that he couldn't kill Koro-sensei.

"I guess that you failed again in Japanese." I dangled my legs off the cliff while looking down.

He stopped what he was doing and glared at me then I heard footsteps and turned around to see Nagisa.

"Karma-kun don't sweat it. We'll all do it together. Once Koro-sensei has his eyes on you, you can't kill him by yourself. No matter the methods you use, he's not like the other teachers."

"Teachers, eh ?" The mercury eyed boy mumbled, I looked at him in confusion and curiosity.

"Karma-kun." Koro-sensei's voice was heard from behind and we all turned to see him. "I've certainly taken good care of you today, haven't I ? You can still try to kill me, and I'll polish you up even shinier." His face changed and green stripes were on it.

Karma stood up carefully on the branch. "I want to make sure... you are a teacher, right ?"

Koro-sensei nodded and I didn't like where this was going.

"And you would risk your own life for one of your students right ?" Koro-sensei nodded again to his question. I looked at Karma to see him smile. "Then I can kill you."

Karma raised his gun and stepped out of the branch to fall, but since I was really close, my balance slipped and I fell too. The smile on my senpai face was a confused frown when he saw me falling but my body wasn't tense at all while I was falling, death didn't bother and I was glad and ready to face it to be honest. I'll be finally free.

"I'll be finally free." I closed my eyes thinking that I'll meet the ground but instead I felt something soft and... sticky ? I opened my eyes to find that the both of us had landed on a yellow sticky web made of the tentacles of our teacher. I was on top of Karma, my head was above his shoulder but I didn't care, the only thought that I had in my mind was that I was alive.

3rd person's POV :

Karma was staring at you wondering what was the meaning of your words then the voice of their sensei was heard. "Good job, Karma-kun. Attempting to do a suicide was a great idea to assassinate me. If I save you at Mach speed, your body wouldn't have supported the impact but if I moved slowly, I'd have been hit. This is why I choose a stickier approach."

Tokoyami looked at Karma's face to see annoyance as he struggled but found out that he couldn't move.

Tokoyami's POV :

I searched for Koro-sensei and gave a polite smile. "Umm... Thanks for saving us Koro-sensei." But the moment was spoiled when Karma grumbled."Damn, what can't these tentacles do ?!" Koro-sensei chuckled. "Now you can't shoot me." He passed through a space in the web so we could see him. "Oh and for the record, letting you die isn't an option for me. Same for you Tokoyami-kun so think of that next time you want to put your or your comrades's life in danger."

Karma's face relaxed at Koro-sensei's words while I looked at the octopus with empty and annoyed eyes but only the concerned of the glare noticed and it surprised him to see such a look on my face. The sun's rays hit the yellow face of the teacher then he put his two students back on the cliff in safety.

"That was crazy you know Karma-kun." Nagisa said while you looking down on the cliff then he turned to me. "And you should be more careful Tokoyami-kun." I laughed nervously while scratching my neck. "Well I lost my balance and that cause me to fall but the important thing is that the both of us are safe."

"You're right."

"It was the only thing I could think at the moment" Karma said bluntly like he didn't just risk his life awhile ago.

I looked at him with a scowl. "You just kind of copied what I did this morning, Bakarma-senpai~." I finished in a sing-song voice and it was now his turn to scowl with the nickname I gave him. Then we heard a chuckle and turned to Koro-sensei.

"Nurufufufu, you've already given up ? But I have many other things to polish you." And we all saw a lot of accessories in his tentacles, we sweatdropped but I had to admit that the cat ears looked cute.

Karma stood up and said confidently. "I'll kill you Koro-sensei. Maybe even tomorrow."

Koro-sensei commented that Karma had a healthy bloodlust and that he didn't need sensei's care anymore with his orange face that had a circle. After that Karma invited Nagisa and me to go while playing with a purse, Koro-sensei recognised his purse and when Karma gave it back it was empty.

"Well I have to go. See you tomorrow senpai, sensei." And I left to go back home.

At home my father was waiting for me on the couch. "Tadaima Father."

"How was your day ?"

"I keep observing the teacher for the rest of the day like you told me to. The red haired known as Karma keept trying to kill him but each attempts failed but I have to admit that he has good potential to kill him and that we could be successful together..."

My father got up of the couch and before I could understand what happened, I was on the floor feeling a stinging sensation on my cheek then it was pain on my stomach then everywhere on my body.

"YOU HAVE TO KILL THIS MONSTER ALONE ! I'M NOT GOING TO SHARE THE MONEY WITH SOME COLLEGIEN ! DO YOU UNDERSTAND ?! YOU HAVE TO GAIN THEIR TRUST BUT TO KILL HIM BY YOUR OWN !"

And this continued on for the next few minutes until my father had enough ad left me here. I got to my room and cleanef myself so nobody would have any suspicions


End file.
